On 12/08/16 11:12, Salah Triki wrote: > ag_shift is used by blockno2iaddr() to get allocation group number > from block. If ag_shift is inconsistent with block_per_ag, an out of > bounds allocation group may occur [1]. So add return BEFS_ERR and update > comment and error message to reflect this change. > > [1] https://lkml.org/lkml/2016/8/12/42 > > Signed-off-by: Salah Triki <salah.triki@xxxxxxxxx> > --- > fs/befs/super.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/befs/super.c b/fs/befs/super.c > index 7c50025..2e3a3fd 100644 > --- a/fs/befs/super.c > +++ b/fs/befs/super.c > @@ -101,10 +101,13 @@ befs_check_sb(struct super_block *sb) > > > /* ag_shift also encodes the same information as blocks_per_ag in a > - * different way, non-fatal consistency check > + * different way as a consistency check. > */ > - if ((1 << befs_sb->ag_shift) != befs_sb->blocks_per_ag) > - befs_error(sb, "ag_shift disagrees with blocks_per_ag."); > + if ((1 << befs_sb->ag_shift) != befs_sb->blocks_per_ag) { > + befs_error(sb, "ag_shift disagrees with blocks_per_ag. " > + "Corruption likely."); > + return BEFS_ERR; > + } > > if (befs_sb->log_start != befs_sb->log_end || > befs_sb->flags == BEFS_DIRTY) { > Hi Salah, I initially also added the BEFS_ERR return for this check. I understand it makes sense. But as I mentioned in the patch adding this warning [0], a correct blocks_per_ag isn't mandatory. I noticed this because BeFS images created by Haiku OS just set blocks_per_ag to 1. Which is clearly not what it should be. The file systems created by Haiku OS can be read without issues since sb->blocks_per_ag isn't actually used in lookups/reading file datastreams. This is what I get in dmesg when loading a Haiku OS image with CONFIG_BEFS_DEBUG on: ... [ 196.376651] befs: (loop1): blocks_per_ag 1 [ 196.376652] befs: (loop1): ag_shift 14 ... With ag_shift of 14, blocks_per_ag should be 16,384. If we return BEFS_ERR, the system will refuse to mount and users won't be able to read these Haiku OS images they could read before. Unfortunate that Haiku OS is not using blocks_per_ag properly, but users and avoiding regressions go first. Which BeFS images are you using to test the befs code? Since all the ones I have are generated from Haiku OS, all of them have a bad blocks_per_ag. LOL Maybe we should contact Haiku OS developers and ask them to write a correct blocks_per_ag. Though we should also support images created before they fix this. Sorry you spent time on this when the issue is out of our control :( Nacked-by: Luis de Bethencourt <luisbg@xxxxxxxxxxxxxxx> Thanks, Luis [0] https://lkml.org/lkml/2016/8/9/816 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
